An adjusting device according to the preamble of claim 1 is evident from DE-AS 1 958 768. An adjusting device, with an actuating piston, which at the same time forms the valve housing for a control valve, is shown in FIG. 7 of this patent. A valve piston in its turn is axially movable inside the axially movable valve housing, control pressure being applied to the valve housing at one end. By application of the control pressure the valve piston is axially displaced, so that a first control edge increases the actuating pressure in an actuating volume and in this case the valve housing serving as actuating piston is axially displaced in the same direction, so that the control edge is again closed. The actuator defining the displacement volume of the piston engine is also adjusted by the same distance, by which the valve piston and the valve housing have been axially displaced. When the control pressure reduces, a readjusting spring displaces the actuating piston in the reverse direction and a second control edge connects the actuating volume to a tank connection. As a result the actuating volume is relieved and the valve housing serving as actuating piston is axially displaced in the same direction as the valve piston. The pressure chamber for the control pressure is separated from a gas volume by a flexible dividing wall, so that the control pressure experiences a certain time buffering.
The disadvantage with the known adjusting device is that the valve housing and the valve piston of the control valve can be manufactured with the necessary precision with only limited axial face to face dimension. Since the axial displacement of the actuating piston and the valve housing directly define the adjustment of the actuator of the piston engine, the regulating distance for the actuator is relatively short. Either the swash plate of the axial piston engine can only be adjusted therefore within relatively minimal limits, or a corresponding translation is necessary.
The object of the invention therefore is to provide an adjusting device for adjusting the swash plate of an axial piston engine with a swash plate construction, in which the setting range of the actuating piston is independent of the setting range of the valve piston of the control valve.
The object is achieved by the characteristic features of claim 1 in conjunction with the generic-forming features.
The invention is based on the finding that by structurally separating actuating piston and control valve a relatively wide setting range of the actuating piston can be achieved with a relatively narrow setting range of the valve piston of the control piston. The necessary reaction between the actuating piston and the valve piston of the control valve takes place not as with the present state of the art through positive engagement by the valve housing of the control valve, but through non-positive engagement by a readjusting spring connecting the actuating piston to the valve piston of the control valve. The solution according to the invention permits an extremely compact design, which can be easily integrated in a location hole of the housing of the axial piston engine.
The sub-claims contain further advantageous embodiments of the invention.
In particular it is advantageous to design the adjusting piston with a pot-shape so that the adjusting piston holds the readjusting spring and a plate spring connected to the valve piston of the control valve.
A communicating channel is preferably provided in the stationary valve housing to connect the actuating volume to the control edges of the valve piston. The valve housing can also have a restrictor, in order to connect the communicating channel restricted to the tank connection and to relieve the actuating volume. In addition the valve piston preferably has a through hole, in order to allow the actuating pressure to act on both sides of the valve housing, so that the position of the valve is independent from the actuating pressure.
The valve housing of the control valve is preferably pressed by a pressure spring against an adjustable stop so that the axial position of the valve housing can be adjusted. The stop can for example be formed by an eccentric stud.
The control force acting on the actuating piston of the control valve is preferably produced by a solenoid, in particular a proportional magnet, or an electric motor, in particular a stepping motor. In this case the solenoid or electric motor can engage the valve piston via a tappet at the end opposite to the readjusting spring.